The polyamines, putrescine, spermidine and spermine are widely distributed in all living cells. They are important for many systems related to growth and differentiation. We have studies how these polyamines are synthesized, how their biosynthesid and degradation are regulated, their physiologic function, and how they are in vivo. For this purpose we have constructed null mutants in each of the biosynthetic steps in both Escherichia coli and Saccharomyces cerevisiae. These mutants are unable to make these amines, and hence, they are very useful toools to study the physiological effects due to their deprivation. Our present studies are directed at extending our studies on the biochemistry, regulation and genetics of these amines and of the biosynthetic enzymes in S. cerevisiae. Our older work has demonstrated that the polyamines are required for growth of the organisms, for sporulation, for maintenance of the killer dsRNA virus, for protection against oxidative damage, for protection against elevated temperatures, for fidelity of protein biosynthesis, and for the maintenance of mitochondria. Clones have been constructed that overproduce the various enzymes, and the sequence and structural characteristics of these enzymes have been studied. Adenosylmethionine decarboxylase has been of particular interest because it is synthesized as a proenzyme that is post-translationally cleaved with the formation of a rather unusual pyruvoyl end group. Our most recent work has concentrated on the structure and regulation of ornithine decarboxylase, spermidine synthase, and spermine synthase.